Consolidated Statements of Income and Comprehensive Income (Unaudited) (Parenthetical) (Unaudited) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Oct. 31, 2014	Oct. 31, 2013	Oct. 31, 2014	Oct. 31, 2013
Income Statement [Abstract]
Other comprehensive income, postretirement benefits, income tax benefit	$ 14	$ 15	$ 40	$ 47